Cu-base amorphous alloy

ABSTRACT

To provide a Cu-based amorphous alloy having a glass-forming ability higher than that of a Cu—Zr—Ti amorphous alloy and a Cu—Hf—Ti amorphous alloy, as well as excellent workability and excellent mechanical properties without containing large amounts of Ti.  
     A Cu-based amorphous alloy characterized by containing 90 percent by volume or more of amorphous phase having a composition represented by Formula: Cu 100-a-b (Zr,Hf) a (Al,Ga) b  [in Formula, a and b are on an atomic percent basis and satisfy 35 atomic percent≦a≦50 atomic percent and 2 atomic percent≦b≦10 atomic percent], wherein the temperature interval ΔTx of supercooled liquid region is 45 K or more, the temperature interval being represented by Formula ΔTx=Tx−Tg (where Tx represents a crystallization initiation temperature and Tg represents a glass transition temperature.), a rod or a sheet having a diameter or thickness of 1 mm or more and a volume fraction of amorphous phase of 90% or more can be produced by a metal mold casting method, the compressive strength is 1,900 MPa or more, the Young&#39;s modulus is 100 GPa or more, and the Vickers hardness is 500 Hv or more.

TECHNICAL FIELD

The present invention relates to a Cu-based amorphous alloy having ahigh amorphous-forming ability, excellent mechanical properties, and ahigh Cu content.

BACKGROUND ART

It is well known that amorphous solids in various shapes, e.g., in theshape of a thin ribbon, a filament, or a powder and granular material,can be produced by rapid solidifying alloys in a molten state. Anamorphous alloy thin ribbon can be prepared by various methods, e.g., asingle-roll process, a twin-roll process, an in-rotating liquid spinningprocess, or an atomization process, which can provide high coolingrates. Therefore, a number of Fe-based, Ti-based, Co-based, Zr-based,Ni-based, Pd-based, or Cu-based amorphous alloys have been developed,and properties specific to amorphous alloys, e.g., excellent mechanicalproperties and high corrosion resistance, have been made clear. Forexample, with respect to Cu-based amorphous alloys, researches have beenmade primarily on binary Cu—Ti or Cu—Zr or ternary Cu—Ni—Zr, Cu—Ag-RE,Cu—Ni—P, Cu—Ag—P, or Cu—Mg-RE.

These Cu-based amorphous alloys have a poor glass-forming ability and,therefore, amorphous alloys of only thin ribbon shaped, powder-shaped,fiber-shaped, and the like have been able to be produced by a liquidquenching technique. Since high thermal stability is not exhibited andit is difficult to form into the shape of a final product, industrialapplications thereof are significantly limited.

It is known that an amorphous alloy exhibits high stability againstcrystallization and has a high amorphous-forming ability, the amorphousalloy exhibiting glass transition and having a large supercooled liquidregion and a high reduced glass transition temperature (Tg/Tl). Such abulk-shaped amorphous alloy can be produced by a metal mold castingmethod. On the other hand, it is known that when an amorphous alloy isheated, transition to a supercooled liquid state is effected beforecrystallization and a sharp reduction in viscosity is exhibited withrespect to a specific alloy system. In such a supercooled liquid state,since the alloy has a reduced viscosity, an amorphous alloy moldedarticle in an arbitrary shape can be produced by a closed forgingprocess or the like. Consequently, it can be said that an alloy having alarge supercooled liquid region and a high reduced glass transitiontemperature (Tg/Tl) has a high amorphous-forming ability and excellentworkability.

Research and development on a large size Cu-based amorphous alloy inconsideration of practical use, put another way, on a Cu-based amorphousalloy having an excellent amorphous-forming ability and a high Cucontent have made little headway. A nonmagnetic elinvar alloy used foran elastic effector has been invented (Patent Document 1), while thealloy is represented by a general formula Cu_(100-a-b-c)M_(a)X_(b)Q_(c)(M represents at least one element of Zr, RE, and Ti, X represents atleast one element of Al, Mg, and Ni, and Q represents at least oneelement of Fe, Co, V, Nb, Ta, Cr, Mo, W, Mn, Au, Ag, Re, platinum groupelements, Zn, Cd, Ga, In, Ge, Sn, Sb, Si, and B). However, specificexamples of compositions include only those containing Cu at contents ofa low 40 atomic percent or less, and with respect to the mechanicalproperties, only an example in which the Vickers hardness (20° C. Hv) is210 to 485 is reported. Furthermore, a nonmagnetic metal glassy alloyused for strain gauges has been invented (Patent Document 2), while thealloy has an alloy composition similar to this.

In 2001, the inventors of the present invention developed a Cu-basedCu—Zr—Ti and Cu—Hf—Ti amorphous alloys having an excellentamorphous-forming ability, and applied for a patent (Patent Document 3).

-   Patent Document 1 Japanese Unexamined Patent Application Publication    No. 09-20968-   Patent Document 2 Japanese Unexamined Patent Application Publication    No. 11-61289-   Patent Document 3 WO 02/053791 A1

DISCLOSURE OF INVENTION

A Cu₆₀Zr₄₀ amorphous alloy has ΔTx=55 K. However the mechanicalproperties, e.g., compressive strength, are not satisfactory. It ispreferable to add 5 to 30 atomic percent of Ti thereto as an element toimprove the amorphous-forming ability. However, the ΔTx of this Cu—Zr—Tiamorphous alloy is about 30 to 47 K and, therefore, it cannot be saidthat the alloy has adequately excellent workability. Although a Cu—Hf—Tior Cu—Zr—Hf—Ti amorphous alloy has a ΔTx larger than that of theCu—Zr—Ti amorphous alloy, a Hf metal is significantly expensive comparedwith a Zr metal and, therefore, is not suitable for practical use.

Accordingly, it is an object of the present invention to provide aCu-based amorphous alloy having a glass-forming ability higher than thatof a Cu—Zr—Ti amorphous alloy and a Cu—Hf—Ti amorphous alloy, as well asexcellent workability and excellent mechanical properties withoutcontaining large amounts of Ti in contrast to the above-describedCu-based amorphous alloy.

In order to overcome the above-described problems, the inventors of thepresent invention conducted research on an optimum composition of theCu-based amorphous alloy, and as a result, found out that an amorphousphase rod (sheet) exhibiting a supercooled liquid region ΔTx of 45 ormore and having a diameter (thickness) of 1 mm or more was able to beattained by melting an alloy having a specific composition containing Zrand/or Hf, Al and/or Ga, and the remainder, Cu, followed by quenchingfrom the liquid state to solidify, and thereby, a Cu-based amorphousalloy having a high glass-forming ability as well as excellentworkability and excellent mechanical properties was able to be attained.Consequently, the present invention was completed.

A Cu-based amorphous alloy according to an aspect of the presentinvention is characterized by containing 90 percent by volume or more ofamorphous phase having a composition represented by Formula:Cu_(100-a-b)(Zr,Hf)_(a)(Al,Ga)_(b) [in Formula, a and b are on an atomicpercent basis and satisfy 35 atomic percent≦a≦50 atomic percent and 2atomic percent≦b≦10 atomic percent], wherein the temperature intervalΔTx of supercooled liquid region is 45 K or more, the temperatureinterval being represented by Formula ΔTx=Tx−Tg (where Tx represents acrystallization initiation temperature and Tg represents a glasstransition temperature.), a rod or a sheet having a diameter orthickness of 1 mm or more and a volume fraction of amorphous phase of90% or more can be produced by a metal mold casting method, thecompressive strength is 1,900 MPa or more, the Young's modulus is 100GPa or more, and the Vickers hardness is 500 Hv or more.

Furthermore, a Cu-based amorphous alloy according to another aspect ofthe present invention is characterized by containing 90 percent byvolume or more of amorphous phase having a composition represented byFormula: Cu_(100-a-b)(Zr,Hf)_(a)(Al,Ga)_(b)M_(c)T_(d)Q_(e) [in Formula,M represents at least one element selected from the group consisting ofFe, Ni, Co, Ti, Cr, V, Nb, Mo, Ta, W, Be, and rare-earth elements, Trepresents at least one element selected from the group consisting ofGe, Sn, Si, and B, Q represents at least one element selected from thegroup consisting of Ag, Pd, Pt, and Au, a, b, c, d, and e are on anatomic percent basis and satisfy 35 atomic percent≦a≦50 atomic percent,2 atomic percent≦b≦10 atomic percent, 0≦c≦5%, 0≦d≦5%, 0≦e≦5%, andb+c+d+e≦15 atomic percent], wherein the temperature interval ΔTx ofsupercooled liquid region is 45 K or more, the temperature intervalbeing represented by Formula ΔTx=Tx−Tg (where Tx represents acrystallization initiation temperature and Tg represents a glasstransition temperature.), a rod or a sheet having a diameter orthickness of 1 mm or more and a volume fraction of amorphous phase of90% or more can be produced by a mold casting method, the compressivestrength is 1,900 MPa or more, the Young's modulus is 100 GPa or more,and the Vickers hardness is 500 Hv or more.

In the above-described compositional formula, (Zr,Hf) refers to Zrand/or Hf, (Al,Ga) refers to Al and/or Ga. Therefore, theabove-described Formula: Cu_(100-a-b)(Zr,Hf)_(a)(Al,Ga)_(b) is any oneof the following formulae.

Cu_(100-a-b)Zr_(a)Al_(b), Cu_(100a-b)Hf_(a)Al_(b),Cu_(100-a-b)Zr_(a)Ga_(b), Cu_(100-a-b)Hf_(a)Ga_(b),Cu_(100-a-b)(Zr+Hf)_(a)Al_(b), Cu_(100-a-b)(Zr+Hf)_(a)Ga_(b),Cu_(100-a-b)(Zr+Hf)_(a)(Al+Ga)_(b)

With respect to the Cu-based amorphous alloy according to the presentinvention, the temperature interval ΔTx of supercooled liquid region is45 K or more, the temperature interval being represented by the formulaΔTx=Tx−Tg (where Tx represents a crystallization initiation temperatureand Tg represents a glass transition temperature.), the reduced glasstransition temperature represented by Tg/Tl (where Tl represents aliquid phase line temperature of an alloy) is 0.57 or more, and a rod ora sheet having a diameter or thickness of 1 mm or more and a volumefraction of amorphous phase of 90% or more can be produced by a metalmold casting method.

In the present specification, the term “supercooled liquid region” isdefined by the difference between a glass transition temperature and acrystallization temperature, which are determined by a differentialscanning calorimetric analysis performed at a heating rate of 40 K perminute. The “supercooled liquid region” is a numerical value indicativeof resistance against crystallization, that is, the stability and theworkability of an amorphous material. The alloys of the presentinvention have supercooled liquid regions ΔTx of 45K or more. In thepresent specification, the term “reduced glass transition temperature”is defined by a ratio of the glass transition temperature (Tg) to analloy liquid phase line temperature (Tl) which is determined by adifferential thermal analysis (DTA) performed at a heating rate of 40 Kper minute. The “reduced glass transition temperature” is a numericalvalue indicative of an amorphous-forming ability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing DSC curves of amorphous bulk materials ofCu—Zr—Al ternary alloys.

FIG. 2 is a graph showing X-ray diffraction patterns of the amorphousbulk materials of the Cu—Zr—Al ternary alloys.

FIG. 3 is a graph showing stress-strain curves based on a compressiontest of the Cu—Zr—Al amorphous alloy bulk materials having a diameter of2 mm.

BEST DESCRIPTION FOR CARRYING OUT THE INVENTION

The embodiments of the present invention will be described below. In theCu-based amorphous alloy of the present invention, Zr and Hf are basicelements to form an amorphous material. The amount of Zr and Hf is 35atomic percent or more and 50 atomic percent or less, and morepreferably, is 40 atomic percent or more and 45 atomic percent or less.

When the amount of Zr and Hf is 35 atomic percent or more, the ΔTxbecomes 45 k or more, and the workability is improved. In particular,when the amount of Zr is 40 atomic percent or more, the ΔTx becomes 50 kor more.

The elements Al and Ga are fundamental elements of the alloys of thepresent invention and, in particular, have the effect of significantlyenhancing the amorphous-forming ability of Cu—(Zr,Hf) alloys. The amountof the elements Al and Ga is 2 atomic percent or more and 10 atomicpercent or less, and more preferably, is 2.5 atomic percent or more and9 atomic percent or less.

The amount of Cu is specified to be 40 atomic percent or more and lessthan 63 atomic percent. If the amount of Cu is less than 40 atomicpercent, the glass-forming ability and the strength are reduced. If theamount of Cu becomes 63 atomic percent or more, the temperature intervalΔTx of the supercooled liquid region is decreased and the glass-formingability is reduced. More preferably, the range is 50 atomic percent ormore and 60 atomic percent or less.

The total amount of Zr, Hf, and Cu is 90 atomic percent or more and 98atomic percent or less. If the total amount is less than 90 atomicpercent, desired mechanical properties cannot be attained. If the totalamount exceeds 98 atomic percent, a shortage of the elements Al and Gato enhance the amorphous-forming ability occurs and, thereby, theglass-forming ability is reduced. More preferably, the range is 91atomic percent or more and 97.5 atomic percent or less.

An addition of small amounts of Fe, Ni, Co, Ti, Cr, V, Nb, Mo, Ta, W, ora rare-earth element to the above-described basic alloy composition iseffective at increasing the strength. However, the amorphous-formingability is deteriorated. Therefore, when the addition is performed, theamount is specified to be 5 atomic percent or less.

An addition of small amounts of element Ge, Sn, Si, Be or B increasesthe range of the supercooled liquid region. However, if the amountexceeds 5 atomic percent, the amorphous-forming ability is deteriorated.Therefore, when the addition is performed, the amount is specified to be5 atomic percent or less.

Furthermore, the range of the supercooled liquid region is increased byan addition of up to 5 atomic percent of an element Ag, Pd, Au, or Pt.However, if the amount exceeds 5 atomic percent, the amorphous-formingability is deteriorated. Therefore, when the addition is performed, theamount is specified to be 5 atomic percent or less. The total of theamount of these additional elements and the amounts of elements Al andGa, that is, b+c+d+e in the above-described compositional formula, isspecified to be 15 atomic percent or less, and more preferably, be 10atomic percent or less. If the total amount exceeds 15 atomic percent,the glass-forming ability is reduced to an undesirable degree.

The Cu-based amorphous alloy of the present invention in a molten statecan be quenched and solidified by various known methods, e.g., asingle-roll process, a twin-roll process, an in-rotating liquid spinningprocess, or an atomization process and, thereby, an amorphous solid inthe shape of a thin ribbon, a filament, or a powder and granularmaterial, can be produced. Since the Cu-based amorphous alloy of thepresent invention has a high amorphous-forming ability, an amorphousalloy in an arbitrary shape can be produced not only by theabove-described known production methods, but also by filling a moltenmetal in a metal mold so as to cast. For example, in a typical metalmold casting method, an alloy is melted in an argon atmosphere in aquartz tube and, thereafter, the molten metal is filled in a copper moldat an ejection pressure of 0.5 to 1.5 Kg·f/cm² and is solidified, sothat an bulk amorphous alloy can be produced. In addition, productionmethods, e.g., a die casting method and a squeeze casting method, canalso be applied.

EXAMPLES

The examples of the present invention will be described below. Motheralloys were prepared through melting from materials having alloycompositions shown in Table 1 (Examples 1 to 23) by an arc meltingmethod. Thereafter, thin ribbon samples of about 20 μm were prepared bya single-roll liquid quenching process. Subsequently, the glasstransition temperature (Tg) and the crystallization initiationtemperature (Tx) of the thin ribbon sample were measured with adifferential scanning calorimeter (DSC). The supercooled liquid region(Tx−Tg) was calculated from these values. The liquid phase linetemperature (Tl) was measured by a differential thermal analysis (DTA).The reduced glass transition temperature (Tg/Tl) was calculated fromthese values. A rod-shaped sample having a diameter of 1 mm was preparedby the mold casting method, and an amorphous state of the sample waschecked by an X-ray diffraction method.

The volume fraction (Vf-amo.) of amorphous phase contained in the samplewas evaluated by using DSC based on the comparison of calorific value ofthe sample during crystallization with that of a completely amorphousthin ribbon having a thickness of about 20 μm. These evaluation resultsare shown in Table 1. Furthermore, a compression test piece wasprepared. A compression test was performed with an Instron type testingmachine, and the compressive strength (σf) and the Young's modulus (E)were evaluated. The Vickers hardness (Hv) was measured. The measurementresults are shown in Table 2.

FIG. 1 shows DSC curves of amorphous bulk materials of Cu—Zr—Al alloys.FIG. 2 shows X-ray diffraction patterns. FIG. 3 shows stress-straincurves based on the compression test of the amorphous bulk materials ofthe Cu—Zr—Al alloys. TABLE 1 T_(x) − Alloy composition T_(g) T_(x) T_(g)T_(g)/ V_(f)- (at %) (K) (K) (K) T_(m) Amo. Example 1 Cu₆₀Zr₃₅Al₅ 755801 46 0.59 100 Example 2 Cu₅₅Zr₄₀Al₅ 723 800 77 0.62 100 Example 3Cu₅₀Zr₄₅Al₅ 701 770 69 0.60 100 Example 4 Cu_(52.5)Zr_(42.5)Al₅ 709 78172 0.61 100 Example 5 Cu₅₅Zr_(42.5)Al_(2.5) 705 773 68 0.61 100 Example6 Cu₅₅Hf₄₀Al₅ 777 862 85 0.60 100 Example 7 Cu₅₀Hf₄₅Al₅ 765 857 92 0.62100 Example 8 Cu_(52.5)Hf₄₀Al_(7.5) 779 834 55 0.63 100 Example 9Cu₅₀Hf_(42.5)Al_(7.5) 780 835 55 0.63 100 Example 10Cu_(52.5)Hf_(42.5)Al₅ 771 849 78 0.59 100 Example 11Cu₅₅Hf_(37.5)Al_(7.5) 776 863 87 0.61 100 Example 12Cu₅₅Hf_(42.5)Al_(2.5) 769 831 62 0.60 100 Example 13Cu₅₀Zr_(22.5)Hf_(22.5)Al₅ 790 843 53 0.62 100 Example 14 Cu₅₅Zr₄₀Ga₅ 730780 50 0.61 100 Example 15 Cu_(42.5)Zr_(42.5)Ga₅ 728 777 49 0.61 100Example 16 Cu₅₅Hf₄₀Ga₅ 784 847 63 0.58 100 Example 17Cu₅₀Zr₄₅Al_(2.5)Ga_(2.5) 728 792 64 0.61 100 Example 18 Cu₄₅Zr₄₅Al₅Ni₅710 775 65 0.59 100 Example 19 Cu₅₀Zr₄₀Al₅Nb₅ 721 771 50 0.61 100Example 20 Cu₅₀Zr₄₀Al₅Au₅ 735 815 80 0.61 100 Example 21 Cu₅₀Zr₄₀Al₅Y₅721 795 74 0.61 100 Example 22 Cu₅₀Zr₄₅Al_(2.5)Sn_(2.5) 707 785 78 0.61100 Example 23 Cu₅₀Zr₄₅Al_(2.5)B_(2.5) 713 792 79 0.61 100 ComparativeCu₇₀Hf₂₀Al₁₀ — — — —  50< example 1 Comparative Cu₇₀Hf₂₀Al₁₀ — — — — 50< example 2 Comparative Cu₅₅Zr₂₀Al₅Ni₁₀ — — — —  50< example 3Comparative Cu₆₀Al₄₀ — — — —  10< example 4 Comparative Cu₆₀Zr₃₀Ti₁₀ 713750 37 0.61 100 example 5 Comparative Cu₆₀Hf₂₀Ti₂₀ 730 768 38 0.61 100example 6 Comparative Cu₆₀Zr₄₀ 717 777 60 0.60  91 example 7 ComparativeCu₅₅Zr₃₅Ti₁₀ 680 727 47 0.59 100 example 8 Comparative Cu₅₃Zr₃₅Al₅Ti₇721 753 32 0.54  50< example 9

TABLE 2 Alloy composition (at %) σ_(f) (MPa) E (GPa) Hv Example 1Cu₆₀Zr₃₅Al₅ 2265 119 603 Example 2 Cu₅₅Zr₄₀Al₅ 2220 116 581 Example 3Cu₅₀Zr₄₅Al₅ 1921 103 546 Example 4 Cu_(52.5)Zr_(42.5)Al₅ 2130 112 568Example 5 Cu₅₅Zr_(42.5)Al_(2.5) 2200 115 589 Example 6 Cu₅₅Hf₄₀Al₅ 2280121 642 Example 7 Cu₅₀Hf₄₅Al₅ 2320 134 667 Example 8Cu_(52.5)Hf₄₀Al_(7.5) 2295 128 644 Example 9 Cu₅₀Hf_(42.5)Al_(7.5) 2372137 673 Example 10 Cu_(52.5)Hf_(42.5)Al₅ 2380 137 681 Example 11Cu₅₅Hf_(37.5)Al_(7.5) 2412 140 698 Example 12 Cu₅₅Hf_(42.5)Al_(2.5) 2253131 692 Example 13 Cu₅₀Zr_(22.5)Hf_(22.5)Al₅ 2130 122 591 Example 14Cu₅₅Zr₄₀Ga₅ 2219 117 585 Example 15 Cu_(52.5)Zr_(42.5)Ga₅ 2100 115 571Example 16 Cu₅₅Hf₄₀Ga₅ 2275 126 652 Example 17 Cu₅₀Zr₄₅Al_(2.5)Ga_(2.5)2205 115 691 Example 18 Cu₄₅Zr₄₅Al₅Ni₅ 2025 107 569 Example 19Cu₅₀Zr₄₀Al₅Nb₅ 2312 131 674 Example 20 Cu₅₀Zr₄₀Al₅Au₅ 2245 117 597Example 21 Cu₅₀Zr₄₀Al₅Y₅ 2180 114 575 Example 22Cu₅₀Zr₄₅Al_(2.5)Sn_(2.5) 2200 112 561 Example 23 Cu₅₀Zr₄₅Al_(2.5)B_(2.5)2175 119 559 Comparative Cu₇₀Zr₂₀Al₁₀ — — 564 example 1 ComparativeCu₇₀Hf₂₀Al₁₀ — — 624 example 2 Comparative Cu₅₅Zr₃₀Al₅Ni₁₀ — — 578example 3 Comparative Cu₆₀Ti₄₀ — — 566 example 4 ComparativeCu₆₀Zr₃₀Ti₁₀ 2115 114 504 example 5 Comparative Cu₆₀Hf₂₀Ti₂₀ 2080 135620 example 6 Comparative Cu₆₀Zr₄₀ 1880 102 555 example 7 ComparativeCu₅₅Zr₃₅Ti₁₀ 1860 112 567 example 8 Comparative Cu₃₅Zr₃₅Al₅Ti₇ — — 584example 9

As is clear from Table 1, with respect to the amorphous alloy of eachExample, the Cu—Hf or Cu—Zr—Hf amorphous alloy exhibits ΔTx of a large50 K or more, even the Cu—Zr amorphous alloy exhibits ΔTx of 45 K ormore, the reduced glass transition temperature of 0.57 or more isexhibited, and an amorphous alloy rod having a diameter of 1 mm wasreadily produced.

On the other hand, in the alloys of Comparative examples 1 and 2,(Al,Ga) is 10 atomic percent while (Zr,Hf) is less than 35 atomicpercent, a high glass-forming ability is not exhibited, and norod-shaped amorphous alloy having a diameter of 1 mm was produced.

In the alloy of Comparative example 3, the amount of Ni exceeds 5 atomicpercent, a high glass-forming ability is not exhibited, and norod-shaped amorphous alloy having a diameter of 1 mm was produced. Inthe alloy of Comparative example 4, no basic element (Zr,Hf) is present,nor was rod-shaped amorphous alloy having a diameter of 1 mm produced.In the alloys of Comparative examples 5 and 6, no fundamental element(Al,Ga) is present. Although an rod-shaped amorphous alloy having adiameter of 1 mm was produced, the supercooled liquid region is lessthan 45 K, and excellent workability is not exhibited.

In the alloys of Comparative examples 7 and 8, Zr is 35 atomic percentor more, the supercooled liquid region is 45 K or more, and excellentworkability is exhibited. However, the compressive strength is small.

In the alloy of Comparative example 9, when Ti exceeded 5 atomicpercent, the reduced glass transition temperature Tg/Tl wassignificantly reduced and, therefore, no rod-shaped amorphous alloyhaving a diameter of 1 mm was produced.

As is clear from Table 2, the amorphous alloy of each Example exhibitsthe compressive fracture strength (σf: MPa) of 1,921 at minimum and2,412 at maximum, the hardness (room temperature Vickers hardness: Hv)of 546 at minimum and 891 at maximum, and the Young's modulus (E: GPa)of 103 at minimum and 140 at maximum, so that the compressive fracturestrength of 1,900 MPa or more, the Vickers hardness of 500 Hv or more,and the Young's modulus of 100 GPa or more are exhibited.

INDUSTRIAL APPLICABILITY

As described above, according to the Cu-based alloy compositions of thepresent invention, rod-shaped samples of 1 mm or more can be readilyprepared by the mold casting method. These amorphous alloys exhibitsupercooled liquid regions of 45 K or more and have high strength andhigh Young's moduli. In this manner, a practically useful Cu-basedamorphous alloy having a high amorphous-forming ability as well asexcellent workability and excellent mechanical properties can beprovided.

1. A Cu-based amorphous alloy comprising 90 percent by volume or more ofamorphous phase having a composition represented by Formula:Cu_(100-a-b)(Zr,Hf)_(a)(Al,Ga)_(b) [in Formula, a and b are on an atomicpercent basis and satisfy 35 atomic percent≦a≦50 atomic percent and 2atomic percent≦b≦10 atomic percent], wherein the temperature intervalΔTx of supercooled liquid region is 45 K or more, the temperatureinterval being represented by Formula ΔTx=Tx−Tg (where Tx represents acrystallization initiation temperature and Tg represents a glasstransition temperature), a rod or a sheet having a diameter or thicknessof 1 mm or more and a volume fraction of amorphous phase of 90% or morecan be produced by a metal mold casting method, the compressive strengthis 1,900 MPa or more, the Young's modulus is 100 GPa or more, and theVickers hardness is 500 Hv or more.
 2. A Cu-based amorphous alloycomprising 90 percent by volume or more of amorphous phase having acomposition represented by Formula:Cu_(100-a-b)(Zr,Hf)_(a)(Al,Ga)_(b)M_(c)T_(d)Q_(e) [in Formula, Mrepresents at least one element selected from the group consisting ofFe, Ni, Co, Ti, Cr, V, Nb, Mo, Ta, W, Be, and rare-earth elements, Trepresents at least one element selected from the group consisting ofGe, Sn, Si, and B, Q represents at least one element selected from thegroup consisting of Ag, Pd, Pt, and Au, a, b, c, d, and e are on anatomic percent basis and satisfy 35 atomic percent≦a≦50 atomic percent,2 atomic percent≦b≦10 atomic percent, 0≦c≦5%, 0≦d≦5%, 0≦e≦5%, andb+c+d+e≦15 atomic percent], wherein the temperature interval ΔTx ofsupercooled liquid region is 45 K or more, the temperature intervalbeing represented by Formula ΔTx=Tx−Tg (where Tx represents acrystallization initiation temperature and Tg represents a glasstransition temperature.), a rod or a sheet having a diameter orthickness of 1 mm or more and a volume fraction of amorphous phase of90% or more can be produced by a metal mold casting method, thecompressive strength is 1,900 MPa or more, the Young's modulus is 100GPa or more, and the Vickers hardness is 500 Hv or more.